Hypoxia-induced hsa_circ_0000826 is linked to liver metastasis of colorectal cancer.

Background hsa_circ_0000826 has been previously linked to CRC through the competing endogenous RNA network; however, the upstream driver of hsa_circ_0000826 elevation remains unknown. In this study, we aim to elucidate the effect of hypoxia-induced hsa_circ_0000826 on CRC tumorigenesis and metastasis. Methods RNA scope assay was used to evaluate the expression of hsa_circ_0000826 in CRC cells under hypoxia condition. The effects of hsa_circ_0000826 on phenotypes of CRC cells were evaluated through cell migration and invasion assay. The nude, AOM-DSS model mice and APC(Min)(/+)mice were used to investigate the relationship between circ_0000826, hypoxia, and CRC in mice. A total of 100 CRC tissue samples, as well as the paired adjacent tissues, were collected, and qRT-PCR assay was used to detect the expression of hsa_circ_0000826 in these samples. Results Hypoxia-induced hsa_circ_0000826 overexpression can increase the malignant phenotypes, tumor formation, and metastasis capability of CRC cells in vitro. mmu_circ_0000826 levels were significantly increased in the CRC tissues from AOM-DSS and APC mice model under hypoxia conditions. Further, the hypoxia-induced upregulation of mmu_circ_0000826 can also promote CRC tumorigenesis and liver metastasis in vivo. The expression of hsa_circ_0000826 in serum was significantly increased in CRC tissues in 100-pair of CRC and according to the adjacent normal tissues by qRT-PCR assays. Moreover, the expression levels of hsa_circ_0000826 in serum of patient with liver metastasis were significantly increased than those without metastasis. Conclusion Our results suggested that hsa_circ_0000826 was induced by the hypoxia in CRC, which can be a potential biomarker of CRC liver metastasis.